The OG is getting updated to the Lite 12S, with the slight component upgrades for higher specs.
The STM32L433CBU6 is currently absolutely unobtainium. It doesn’t exist in stock, anywhere.
Even in STM’s own store it’s out-of-stock.
I also checked for the bigger flash version, STM32L433CCU6 with 256KB flash (CBU6 has 128KB flash) and the higher temperature rated one, STM32L433CCU3 instead, but both are also unobtainium.
So, unfortunately, and also to my big disappointment, the next build batch is completely on hold. Sorry.
I took inventory and I have 5 units of the MCU, but I think I’ll hold on to those for any possible repairs.
I also looked into different packaging of the MCU, like the TQFP- and WLCSP-packages, but they are also very low on availability. The TQFP, would require a bigger PCB, as it needs more real estate and to be able to use the WLCSP needs BGA level HDI (High Density Integration) for the board design and that requires some special pcb fabrication requirements.
The WLCSP-package with 49 balls (7x7 grid) would be smaller at ~3.3x3.3mm outline compared to the 48-pin QFN package at 7x7mm outline, but the pitch is an insane 0.4mm (distance between the balls on the bottom) that it requires a specialized PCB design and I have attached a video below that demonstrates the insanity of such a small package, with such many balls.
That is an inductor whine from the buck-regulator and it’s normal for this application with the used components.
The inductor’s magnet wire is slightly vibrating with the ON-OFF pulses (EMF causes a physical force to be enacted on the wire) and it has just enough movement that it transmits into the surrounding air, which in this case is a high pitch whine. During the boot-up sequence with the color sequence, you can hear the pitch of the whine slightly change with each different color on the LED, as the current flow changes ever so slightly between the different color diodes being turned on.
